APPENDIX 561 



to destroy- the brain and backwards into the neural canal). 

 Arrange the animal so that one foot lies with the web 

 spread out under the objective of a microscope. With 

 the low power note the circulation in the capillaries 

 (Fig. 29). 

 /. Skin the leg of the same frog. Stimulate the gastrocnemius 

 muscle (Fig. 21) — (1) by pinching, (2) by touching with a 

 hot needle, (3) by a drop of dilute acid. Note contraction of 

 the muscle in consequence of these mechanical, thermal, and 

 chemical stimuli. 1 Dissect out the sciatic nerve (which may 

 be traced back from the abdominal cavity) and apply to it 

 the same stimuli. Note contraction of muscles. 

 II. In the spring, obtain some spawn and preserve a portion of it 

 in 2 per cent, formalin solution or 7° per cent, alcohol. 

 Keep the rest in a large vessel of water with living water 

 weeds. Watch the hatching and growth of the tadpoles, 

 preserving some at every stage. Examine carefully and 

 note : cleavage (Fig. 366) ; gastrulation (Fig. 368) ; and the 

 history of the neural folds, sucker, mouth, gill-clefts, gills, 

 operculum, limbs, and tail (Figs. 6, 370, 372, 373, 375): 

 Good specimens of Amoeba proteus are not always easy to obtain. 



.__. __» u _ They should be looked for at the surface of 



Amoeba, Entamoeba, ,/ , , , . , - ... ., 



Polytoma, Euglena undisturbed, clean pond-mud containing the 



Hamatococcus, Opallna, minute plants on which the animal principally 

 Paramecium, Balantidium, f ee <j s spo t s i n which they are plentiful being 

 MonScJItief' Vortioella ' usually distinguished by a whitish tinge from 

 their browner surroundings. The species of 

 Entammba which is most convenient for laboratory purposes is E. 

 blattcei found among the contents of the rectum of the cockroach. In 

 cold weather, the cockroach should be obtained from some warm 

 place, such as a bakehouse. Polytoma occurs with allied organisms 

 in water which is very foul with decaying animal matter, as in the 

 macerating tub in which bones are prepared for mounting as skeletons ; 

 Euglena in the green water which sometimes fills small ponds and 

 hoof-prints ; Hcematococcus in the rain-water in gutters, etc. ; Opalina, 

 Balantidium, and Nyctotherus in the upper part of the rectum of the 

 frog; Paramecium in hay infusions or similar solutions of decaying 

 vegetable matter (p. 129). Vorticella may be found plentifully growing 

 on objects in ponds and streams, as, for instance, on willow roots. 

 Monocystis will generally be found on opening the vesiculse seminales 

 of a well-grown earthworm, the large species hanging on to the funnels 

 of the vasa deferentia as white threads visible' to the naked eye, the 

 smaller more often free in the contents of the vesiculse, which must be 

 mounted and examined, to find also the cysts, with various stages of 

 conjugation and spore formation. 



I. Examineeach of these Protozoa alive; (a) with the naked eye, 

 if possible, to note the true size, (6) with low power, (c) 

 with high power. Free living forms should be mounted in 



1 This experiment does not prove the irritability of the muscle fibres independent 

 of the nerve endings upon them unless the latter have first been numbed, as by 

 the injection of the poison curari into a lymph sac of the frog. 



